1. Field of the Invention
The present invention relates to an optical element, in particular to a light guiding diffuser.
2. Description of Related Art
The rapid development of the efficiency of the light emitting diode leads to more and more general lighting applications. Besides, light emitting diode has advantages of energy saving, compact size and light weight which make the light emitting diode popular in various fields of illuminating such as indoor or outdoor illuminating and lighting of mobile electronics.
Since the brightness provided by single light emitting diode is usually not enough for most applications, it is necessary to put a plurality of light emitting diodes together in a module to provide appropriate brightness for a specific application. However, the light emitted by each light emitting diode has a limited divergence angle. That means that when the light of the module is projected on the ground or table, it concentrates on a specific area and thus a uniform illumination can not be obtain.
In order to solve the abovementioned issue, an additional optical diffuser is often adopted to expand the divergence angle of the light emitting diode. Such an optical diffuser is also called a secondary lens, which is positioned over the packaged light emitting diode to expand the divergence angle so as to obtain a more uniform illumination. However, the conventional optical diffuser still can not provide a uniform illumination like the illumination provided by a fluorescent lamp.